Lead has been used as a material in bullets for years, and many lead bullets have a nose portion with a hollow point or hollow cavity that enables the bullet to mushroom or petal upon impact with a target. Such mushrooming disperses most or all of the bullet's kinetic energy to the target. Lead has been widely used because it has a high density, good ductility, and low cost. However, there have been assertions that lead bullets present an issue of significant environmental contamination. There have also been claims that scavenger animals, such as the California condor, may have been subjected to lead poisoning from consuming animals shot with lead projectiles.
Bullet manufacturers have attempted to solve these purported problems in various ways. One such solution is to encase a lead core with a non-lead metal. For example, U.S. Pat. No. 5,127,332 discloses a hunting bullet with an encapsulated lead core that purports to minimize contamination of animal tissue. However, certain jurisdictions have entirely banned the use of bullets with any lead for hunting certain game.
Another solution is a completely lead-free bullet. U.S. Pat. No. 4,685,397, for example, discloses a completely lead-free bullet preferably made of tombac that has a cylindrical cavity in the nose and a cap. However, such lead-free bullets generally do not have consistent performance characteristics over a wide range of velocities and uses because the materials do not have the same properties as lead. More specifically, if the opening at the nose of the bullet is too large, or if the cylindrical cavity is too deep, then the bullet may mushroom to the extent that the petals fragment from the bullet upon impact. This can reduce the efficacy of the bullet. Conversely, if the opening at the nose of the bullet is too small, then the bullet may not petal adequately upon impacting a target at low velocity. This also reduces the efficacy of the bullet.
Accordingly, a lead-free bullet that has consistent performance characteristics over a wide range of velocities and uses would have significant utility.